Tanks are commonly equipped with a liquid level switch assembly having a float arm pivotally connected to a stationary arm which is mounted to the tank. The entire float arm can be buoyant or a float can be attached to the float arm at some point. The float arm pivots in response to fluctuations in the liquid level in the tank. Some switch assemblies of this type have a magnet fixed to one arm and a magnetically actuated switch fixed to the other such that when the float arm has pivoted to a predetermined angular position relative to the stationary arm, the magnet will actuate the magnetic switch. Such a switch assembly is shown in U.S. Pat. No. 4,513,185.
A significant drawback of this type of switch assembly is that the angular position of the float arm relative to the stationary arm at which the magnet actuates the switch is not adjustable. Such non-adjustable switches are severely limited in their ability to be adapted to different applications such as different size tanks or different liquid levels at which it is desired for the switch to be actuated. For example, the design of a switch assembly developed to be actuated by a low liquid level of two inches in a two foot deep tank will minimally contain the following elements: 1) the length of the stationary arm; 2) the mounting position of the stationary arm on the tank; 3) the length of the float arm; and 4) the position of the float arm relative to the stationary arm at which the magnet will actuate the switch. However, if the liquid level at which the switch is desired to be actuated is changed from two inches to five inches, or if some of the tanks are two and a half feet deep instead of two feet, the design developed for the two inch, two foot application can not be readily adapted for these new applications. In order to provide a switch for the new applications, one or more of the four basic elements of the design will have to be changed. However, changing the lengths of the arms or the position of the switch assembly on the tank can involve repeated expensive design, component, manufacturing and/or installation changes for each new application that is encountered.
Thus, a need exists for a switch assembly which can be readily adapted for a wide range of applications without having to change the size of its components or its position on the tank. The present invention provides for a switch assembly in which the angular position of the float arm relative to the stationary arm at which the magnetic switch is actuated is readily adjustable, thus allowing the present invention to be readily adapted to a wide range of applications without having to change its structure or its position on the tank.
The advantages of the present invention include the ability to develop a switch assembly that can be easily adjusted for use in a wide range of applications instead of having to change the design, structure and/or installation of the switch assembly for each different application. Additionally, such an adjustable switch assembly greatly simplifies the manufacture of several assemblies in that the same components and manufacturing procedures will be used for each assembly and do not nave to be repeatedly altered to make a different switch assembly for each different application.